qiskit.circuit.library.z_feature_map
qiskit.circuit.library.z_feature_map(feature_dimension, reps=2, entanglement='full', alpha=2.0, data_map_func=None, parameter_prefix='x', insert_barriers=False, name='ZFeatureMap')
The first order Pauli Z-evolution circuit.
On 3 qubits and with 2 repetitions the circuit is represented by:
┌───┐┌─────────────┐┌───┐┌─────────────┐
┤ H ├┤ P(2.0*x[0]) ├┤ H ├┤ P(2.0*x[0]) ├
├───┤├─────────────┤├───┤├─────────────┤
┤ H ├┤ U(2.0*x[1]) ├┤ H ├┤ P(2.0*x[1]) ├
├───┤├─────────────┤├───┤├─────────────┤
┤ H ├┤ P(2.0*x[2]) ├┤ H ├┤ P(2.0*x[2]) ├
└───┘└─────────────┘└───┘└─────────────┘This is a sub-class of PauliFeatureMap where the Pauli strings are fixed as [‘Z’]. As a result the first order expansion will be a circuit without entangling gates.
Examples
>>> prep = z_feature_map(3, reps=3, insert_barriers=True)
>>> print(prep)
┌───┐ ░ ┌─────────────┐ ░ ┌───┐ ░ ┌─────────────┐ ░ ┌───┐ ░ ┌─────────────┐
q_0: ┤ H ├─░─┤ P(2.0*x[0]) ├─░─┤ H ├─░─┤ P(2.0*x[0]) ├─░─┤ H ├─░─┤ P(2.0*x[0]) ├
├───┤ ░ ├─────────────┤ ░ ├───┤ ░ ├─────────────┤ ░ ├───┤ ░ ├─────────────┤
q_1: ┤ H ├─░─┤ P(2.0*x[1]) ├─░─┤ H ├─░─┤ P(2.0*x[1]) ├─░─┤ H ├─░─┤ P(2.0*x[1]) ├
├───┤ ░ ├─────────────┤ ░ ├───┤ ░ ├─────────────┤ ░ ├───┤ ░ ├─────────────┤
q_2: ┤ H ├─░─┤ P(2.0*x[2]) ├─░─┤ H ├─░─┤ P(2.0*x[2]) ├─░─┤ H ├─░─┤ P(2.0*x[2]) ├
└───┘ ░ └─────────────┘ ░ └───┘ ░ └─────────────┘ ░ └───┘ ░ └─────────────┘>>> data_map = lambda x: x[0]*x[0] + 1 # note: input is an array
>>> prep = z_feature_map(3, reps=1, data_map_func=data_map)
>>> print(prep)
┌───┐┌──────────────────────┐
q_0: ┤ H ├┤ P(2.0*x[0]**2 + 2.0) ├
├───┤├──────────────────────┤
q_1: ┤ H ├┤ P(2.0*x[1]**2 + 2.0) ├
├───┤├──────────────────────┤
q_2: ┤ H ├┤ P(2.0*x[2]**2 + 2.0) ├
└───┘└──────────────────────┘>>> from qiskit.circuit.library import TwoLocal
>>> ry = TwoLocal(3, "ry", "cz", reps=1).decompose()
>>> classifier = z_feature_map(3, reps=1) + ry
>>> print(classifier)
┌───┐┌─────────────┐┌──────────┐ ┌──────────┐
q_0: ┤ H ├┤ P(2.0*x[0]) ├┤ RY(θ[0]) ├─■──■─┤ RY(θ[3]) ├────────────
├───┤├─────────────┤├──────────┤ │ │ └──────────┘┌──────────┐
q_1: ┤ H ├┤ P(2.0*x[1]) ├┤ RY(θ[1]) ├─■──┼──────■──────┤ RY(θ[4]) ├
├───┤├─────────────┤├──────────┤ │ │ ├──────────┤
q_2: ┤ H ├┤ P(2.0*x[2]) ├┤ RY(θ[2]) ├────■──────■──────┤ RY(θ[5]) ├
└───┘└─────────────┘└──────────┘ └──────────┘Parameters
- feature_dimension (int) –
- reps (int) –
- entanglement (str | Sequence[Sequence[int]] | Callable[[int], str | Sequence[Sequence[int]]]) –
- alpha (float) –
- data_map_func (Callable[[Parameter], ParameterExpression] | None) –
- parameter_prefix (str) –
- insert_barriers (bool) –
- name (str) –
Return type
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